There are a considerable array of tools available for the modern gardener in order to be able to keep growth of vegetation under control. The term “gardener” is meant not only to encompass small domestic concerns, but also larger more agricultural endeavours. Whatever the nature of the gardening, however, there will be a need to control the rate of growth of vegetation for either aesthetic or other purposes such as crop yields etc.
Among the many tools available for keeping vegetation growth under control are, for example, shears for pruning or cutting “light” vegetation such as grass or leaves or small twigs etc. Shears operate by pivoting a pair of blades located in parallel planes relative to each other so that shear forces are applied to vegetation placed in the angle between the blades, the cutting force being generated by manual force of the user, applied to handles attached to the blades. The size or thickness of vegetation which can be cut by shears is limited to the amount of manual force which can reasonably be applied to the handles by the average user. Known shears also suffer from the disadvantage that the act of pivoting the arms of the shears relative to each other to effect cutting tends to push vegetation being cut away from the gap between the blades of the shears, which makes the it more difficult tot effect cutting of the vegetation.
At the other end of the scale there are hedge trimmers and the so-called chain saw used for “heavy” vegetation cutting such as trees (whether smaller branches or the entire tree).
Additionally there are smaller-scale tools such as secateurs or scissors used for more delicate pruning or cutting operations.
In any event it will be appreciated that the modern gardener will more usually choose a tool specific to the particular type of pruning operation required. For example, and with reference to the above, when light pruning is necessary of, for example, domestic flowers, then the secateurs are likely to be chosen. Alternatively if bushes are to be pruned, or grass is to be cut, then shears will often be chosen.
There exists, however, a gap in the tool array when moving from “light” bushes to “heavy” trees. Very often vegetation will be of such a size and nature (such as larger bushes or small trees) which are either of a density or branch diameter too large for shears or hedge trimmers to cope with but for which use of the chain saw is unnecessarily excessive.
It is, therefore, an object of the present invention to provide a vegetation pruning device which at least alleviates the above shortcomings by providing a novel form of tool which fits nicely in this gap. Provision of such a tool provides a compact and safe arrangement whereby pruning of the “heavier” vegetation is possible without the need to resort to the aggressive and particularly dangerous tool such as a chain saw.
A known type of chain saw is disclosed in U.S. Pat. No. 4,294,012 and has a guard pivotable relative to a blade of the chain saw and located in a plane parallel to the plane of the chain saw blade, to enable the blade to either be inserted beneath a log to be sawn, to reduce the tendency of the sawn piece of log to pinch the chain saw blade, or to grasp small branches to be sawn and force them into the chain saw. The chain saw has a first handle arranged on the chain saw body, and a second handle connected to the guard, so that the guard can be pivoted relative to the chain saw blade by pivoting the handles relative to each other.
However, this arrangement suffers from a number of drawbacks. Firstly, the handles of the chain saw of U.S. Pat. No. 4,294,012 are arranged along axes generally perpendicular to each other, and perpendicular to the axis about which the guard pivots relative to the chain saw blade. As a result, when the chain saw is in use, a user's wrists face directions generally perpendicular to each other, which results in sidewards twisting torque being applied to the chain saw. This reduces the amount of control the user has over the chain saw, which makes it significantly more difficult to cut accurately and safely with the chainsaw. This drawback is exacerbated when a gripping force is applied to the guard to grip a branch being sawn between the guard and the chain saw blade. In addition, the first handle of the arrangement of U.S. Pat. No. 4,294,012 is generally in the same plane as the chain saw guard, whereas the second handle is spaced from the plane of the guard in the direction of the pivot axis. This also exacerbates the extent to which sideward twisting torque is applied to the chain saw when in use, which causes undesirable reduction in control of the chain saw.
Devices for adjusting the tension of a chain saw when the chain becomes slack through wear are also known. For example, U.S. Pat. No. 6,560,879 discloses a chain saw in which a cutting chain is supported on a guide bar and driven around the guide bar by means of a drive sprocket located on the chain saw housing and is driven around an idler sprocket located on the guide bar. The guide bar is releasably held in position relative to the housing by means of cooperating friction surfaces on a locking plate mounted on the guide bar and a cover plate located between the guide bar and a cover assembly, such that when the cooperating friction surfaces are in their released condition, a tensioner pin is caused by a cam biased by means of a torsion spring urges the guide bar away from the housing so that the drive and idler sprockets are urged apart to keep the chain taut.
This arrangement suffers from the drawback that the use of a cam and torsion spring makes the chain saw more complicated and therefore more expensive to construct.